Gas chromatography (GC) remains one of the most important and widely used analytical testing techniques performed today across a number of industries. Growing demands on
the speed and sensitivity of modern testing methods for GC has led to more sophisticated analytical
instrumentation and the increasing prevalence of gas
chromatography mass spectrometry (GCMS) and
other GC techniques. Though this is a common thread among a varied base
of analytical testing laboratories, unique challenges are faced in each industry.

Traditional approaches to dealing with these challenges through the use of
general-purpose GC column technologies have typically yielded only small
strides, such as a 15 percent improvement in run time or sensitivity. Selectivity
is of extreme importance in advancing GC testing methodologies. Application-specific GC column stationary phases in the forensics, fuels and environmental
industries can lead to potential performance and productivity gains.

The end goal in gas chromatography separations is accurate identification or quantification of a laboratory’s compounds of interest. This is
achieved through several means, one of which is resolution. Resolution (R)
is impacted by efficiency (N), selectivity (a) and retention (k), as seen in the
master resolution equation (Figure 1).

Traditional approaches to improving resolution have often focused on
the efficiency of GC columns through manipulation of a column’s length.
Efficiency is directly proportional to length, so longer columns will provide

higher resolution. Based on the master equation;however, resolution is proportional to the squareroot of efficiency. This means that large increasesin efficiency will not necessarily result in a signifi-cant improvement in separation, although theywill have direct impact on run times and resultinglab throughput. For example, doubling a column’slength will approximately double the analysis time,A key to unlocking the true separation power of the GC column lies in thestationary phase. A GC column's stationary phase selectivity has the largest,most direct impact on resolution. This selectivity depends on the nature ofthe stationary phase, the nature of the components and the oven temperatureat the time of elution. It is the most influential GC column criterion, as it notonly determines the final resolution obtained, but also influences virtuallyevery column selection parameter. By increasing the resolution between twocompounds through optimization of the stationary phase selectivity, otherparameters may be altered to allow significant reductions in the total analysistime, while maintaining or improving the original accuracy and sensitivity ofa method. This allows laboratories to more quickly and effectively reach theirseparation goals and improve overall productivity.

Forensic toxicology

Unlike pure samples (such as a bag of cocaine or a pseudoephedrine pill),biological samples (from blood, urine or hair),generally used in drugs of abuse testing, containcontaminants from proteins, red blood cells orsalts that interfere with the analysis and yieldfalse or inaccurate results. These compounds arealso inherently difficult to analyze because oftheir chemically reactive properties, and peaksoften tail on general purpose columns.

Chemists performing these tests have traditionally used varying GC phases, from a non-polar 100 percent dimethylpolysiloxane phase
to a more polar 50 percent phenyl phase.
With these general purpose GC stationary
phases, long run times are traditionally needed to fully resolve the drugs of interest from
contaminants of similar molecular weights
or masses, adding to sample backlogs and